Electric slag remelting process and apparatus for producing metal ingots having a change in transverse dimension

ABSTRACT

A plurality of superimposed ingot molds are provided, which have open ends and differ in at least one inside transverse dimension. A slag layer is provided in said ingot molds. Electrode means which consist of a metal from which an ingot is to be formed are maintained dipped in said slag layer in each of said ingot molds for a period of time while electric current is passed through said electrode means to generate heat and thus fuse down said electrode means in each of said ingot molds to form molten metal therein. Said molten metal is solidified in each of said ingot molds, whereby an integral, rigid ingot is formed.

United States Patent Plockinger et a1. Feb. 22, 1972 PROCESS ANDAPPARATUS FOR UNITED STATES PATENTS PRODUCING METAL INGOTS HAVING ACHANGE IN TRANSVERSE lslopkins DIMENSION unnen FOREIGN PATENTS ORAPPLICATIONS [72] Inventors: Erwin Plockinger; Wolfgang Holzgruber;1,103,350 2/ 1968 Great Britain... ..164/252 Adolf Schneidhofer, all ofKapfenberg, Austria Primary Examiner-J Spencer Overholser AssistantExaminer-John E. Roethel [73] Assignee. Gebr. Bohlen & Co.Aktlengesellschaft, Altamey Armur G Klein Vienna, Austria [22] Filed:Nov. 10, 1969 [57] ABSTRACT [21] Appl. No.: 875,397 A plurality ofsuperimposed ingot molds are provided, which have open ends and differin at least one inside transverse dimension. A slag layer is provided insaid ingot molds. Electrode means which consist of a metal from which aningot is to [30] Foreign Apphcauon Pnomy Data be formed are maintaineddipped in said slag layer in each of Nov. 15, 1968 Austria ..A 11116/68said ingot molds for a period of time while electric current is passedthrough said electrode means to generate heat and thus [52] US Cl..164/52, 164/ 136, 164/252 fuse down said electrode means in each ofsaid ingot molds to [51] Int. Cl ..B22d 27/02 form molten metal therein.Said molten metal is solidified in [58] Field of Search ..164/52, 133,136, 252, 129, each of said ingot molds, whereby an integral, rigidingot is 164/ 130 formed.

15 Claims, 1 Drawing Figure I 57 '1- i 1 80 i i I V 50 30 if m Jami l; la" t 1| l -d [l '34 35 i l L'i .l \L

A 75 n j 20 i /70 i 2ll l 55 I 4 -24 r; l 12 C -d, l l 13 z 5 5' 1 7 71l 82- 1| I ELECTRIC SLAG REMELTING PROCESS AND APPARATUS FOR PRODUCINGMETAL INGOTS HAVING A CHANGE IN TRANSVERSE DIMENSION This inventionrelates to a process of producing ingots which consist of metal,preferably steel, and have considerable changes in cross section ortransverse dimensions, which process comprises an electric slagremelting step, and a plant for carrying out such process. Such ingotsmay serve, e.g., as workpieces to be forged or as workpieces from whichrolls are made.

lt is an object of the invention to enable a production ofingots whichconsist of metal, preferably steel, and have considerable changes incross section or transverse dimensions in a continuous operation byelectric slag remelting. In a process of the kind defined firsthereinbefore, this object is accomplished in that one or moreelectrodes, consisting of the metal to be remelted and disposed under aslag layer, have current conducted therethrough, and under the action ofthe heat which is generated by said current, are fused down insuccession in two or more superimposed ingot molds, which are open atboth ends and have cross sections and transverse dimensions whichcorrespond to those of the ingot to be made. The molten metal is cooledin the ingot mold in which it has been formed so that the molten metalsolidifies to form a single, rigid ingot.

The present process will now be fully described in connection with aplant for carrying out the process. Said plant is diagrammatically shownon the accompanying drawing partly in elevation and partly in section.

An electrode 40 to be fused down is coaxial with cylindrical innershells 11, 21 and 31 of three superimposed ingot molds 10, 20 and 30.Each ingot mold 10, 20 or 30 is secured to a separate mold-liftingcarriage 14, 24 or 34, respectively. An extension rod 41, connected tothe top end of the electrode 40, is secured to an arm portion 51 of anelectrode-lifting carriage 50. The mold-lifting carriages 14, 24 and 34and the electrode-lifting carriage 50, disposed over the mold-liftingcarriages 14, 24 and 34, are vertically displaceable independently ofeach other on the square-section column 60 with the aid of tensioncables, which are not shown. As the electrode 40 is fused down, it canbe adjusted in height so that the electrode 40 dips into the slag layer75, which floats on the molten metal 74 and serves to purify and shieldthe molten steel, and the end of the electrode 40 is spaced the correctdistance apart from the surface of the molten metal 74. At the sametime, the elevation of the ingot molds 14, 24 and 34 may be changed asfollows: During the initial phase of the melting operation, thelowermost ingot mold rests on the liquidcooled bottom plate 82 until thesurface of the molten metal 74 in that ingot mold 10 has reached apredetermined level. The ingot mold 10 is then raised at such a speedthat the relation of the surface of molten metal 74 to the ingot mold 10remains unchanged. The upward movement of the mold 10 is continued untilit contacts the second ingot mold 20, which is disposed over the ingotmold 10. The two ingot molds 10 and now remain at rest until the surfaceof the molten metal 74 in the second ingot mold 20 has reached a certainlevel. The second ingot mold 20 is much larger in inside diameter thanthe lowermost, first ingot mold 10. The second ingot mold 20 is thenraised at such a speed that the relation of the surface of the moltenmetal 74 to the ingot mold 20 remains unchanged. The operation which hasjust been described is then repeated with the uppermost, third ingotmold 30, which is smaller in inside diameter than the second ingot mold20. The remelting operation which has been described thus results in asingle ingot 70, which consists of three cylindrical portions 71, 72,and 73. The two end portions 71 and 73 of the ingot are much smaller indiameter (d and d respectively) than the intermediate portion 72 havinga diameter d,. The complete metal ingot 70 is indicated with dash-dot ordotted lines. The positions assumed by the ingot molds 20 and 30 at theend of the remelting operation are indicated with dash-dot lines. Anelectric lead 80 leads from one terminal of the source of power which isemployed to the extension rod 41 of the electrode 40.

The other terminal of the source of power is connected by an electriclead 81 to the horizontal bottom plate 82, which consists of metal,preferably copper. The source of power is not shown and may consist,e.g., of the secondary winding of a transformer. The bottom of thesolidified ingot rests on the bottom plate 82.

For the sake of completeness, it may be stated that the ingot molds 10,20 and 30 are cooled with water, which flows respectively through thejacket space 13, 23 or 33 defined between the cylindrical inner shell11, 21 or 31 and the outer shell 12, 22, and 32 of each ingot mold 10,20 or 30. Flexible tubes, not shown, are used to conduct cooling waterto and from these jacket spaces 13, 23 and 33.

When the melting operation in one of the ingot molds has beenterminated, warm cooling water may be used to avoid an excessive coolingof the previously solidified ingot portion. Alternatively, split ingotmolds may be used, which are swung open and thus separated from theingot to avoid a continued cooling of the sides of the solidified ingotportion. The solidified ingot portion may be additionally maintained ata predetermined temperature by the application of split insulation,which may be heated or unheated.

The mold-lifting carriages, on the one hand and the electrode-liftingcarriage, on the other hand, may be mounted on separate columns.

The ingots, which are made in the plant which has just been described,are circular in cross section. The present process may also be used,however, to make ingots having other cross sections, which may be, e.g.,rectangular or square, provided that suitably shaped ingot molds areemployed.

The process according to the invention enables the production of ingotswhich consist of metal, preferably steel, and which have considerablechanges in cross section and are of high purity, by electric slagremelting. Where the plant according to the invention is used, thelength of these ingots may be as long as desired within wide limits.

Although the invention is illustrated and described with reference toone preferred embodiment thereof, it is to be expressly understood thatit is in no way limited to the disclosure of such a preferredembodiment, but is capable of numerous modifications within the scope ofthe appended claims.

We claim:

1. A process for casting metal ingots, having at least one change incross-sectional area dimensions, by electroslag remelting electrodemeans, comprising the steps of movably suspending at least two molds ofdifferent crosssectional area dimensions from a vertical column,providing a liquid slag layer in said molds,

movably suspending said electrode means from said vertical column intosaid slag layer,

maintaining said electrode means in said slag layer while passing anelectric current through said electrode means, thereby remelting saidelectrode means by generating heat,

moving a first lower mold of said two molds upwardly jointly with saidelectrode means along said vertical column until said lower mold comesinto contact with the second upper mold of said two molds while themolten metal in said first mold solidifies, and

moving thereafter said second mold upwardly jointly with said electrodemeans along said vertical column, whereby a solid unitary ingot isformed having at least one change in cross-sectional area dimensions.

2. A process as set forth in claim 1, in which said metal is steel.

3. A process as set forth in claim 1, in which said two molds have innercylindrical surfaces of different diameters.

4. A process as set forth in claim 1, in which said electrode meansconsist of a single electrode.

5. A process as set forth in claim 1, in which at least three molds aremovably suspended from said vertical column.

6. A process as set forth in claim 1, which comprises removing saidelectrode means from one of said molds,

cooling said molten metal in said one mold at a first rate until saidmolten metal in said one mold has solidified to form an ingot portion,and

cooling said ingot portion at a second rate, which is lower than saidfirst rate.

7. A process as set forth in claim 6, in which cold water is used tocool molten metal in said one mold at said first rate, and

warm water is used to cool said ingot portion at said second rate.

8. A process as set forth in claim 1, which comprises removing saidelectrode means from one of said molds,

cooling said molten metal in said one mold until said molten metal insaid one mold has solidified to form an ingot portion, and

maintaining said ingot portion at a predetermined temperature.

9. A process as set forth in claim 8, which comprises applying splitinsulation to said ingot portion to maintain it at said predeterminedtemperature.

10. A process as set forth in claim 9, which comprises heating saidinsulation while it is applied to said ingot portion.

11. A process as set forth in claim 1, which comprises removing saidelectrode means from one of said molds,

cooling said molten metal in said one mold until said molten metal insaid one mold has solidified to form an ingot portion, and

applying unheated, split insulation to said ingot portion.

12. In an apparatus for casting molten metal derived from metallicelectrode means extending into a liquid slag layer through which anelectric current is passed, an arrangement comprising a vertical column,at least two molds movably suspended for independent movement on saidvertical column, said two molds having different cross-sectional areadimensions, means for moving said metallic electrode means movablymounted on said column and supporting said electrode means so that itextends into said liquid slag layer, means for moving said two moldscomprising means for moving a first lower mold of said two moldsupwardly jointly with said electrode means along said vertical columnuntil said lower mold comes into contact with the second mold of said momolds while the molten metal in said first lower mold solidifies andmeans for moving said second mold upwardly jointly with said electrodemeans along said vertical column whereby a solid unitary ingot is formedhaving at least one change in cross-sectional area dimensions.

13. The arrangement as set forth in claim 12, which comprises a bottomplate disposed under said molds, said means for moving said moldsincluding a plurality of mold-lifting carriages, each of which carriesone of said molds, said means for moving said electrode means includingan electrode-lifting carriage disposed over said mold-lifting carriagesand carrying said electrode means, and tension cable means operable tocontrol the vertical movement of said mold-lifting carriages and saidelectrode-lifting carriage independently of each other along saidvertical column 14. The arrangement as set forth in claim 13, includingcooling means which are operatively mounted on said two molds and whichare operable to cool said molds with a liquid.

15. The arrangement as set forth in claim 12, in which at least oneofsaid molds is split and adapted to be swung open.

1. A process for casting metal ingots, having at least one change incross-sectional area dimensions, by eLectroslag remelting electrodemeans, comprising the steps of movably suspending at least two molds ofdifferent crosssectional area dimensions from a vertical column,providing a liquid slag layer in said molds, movably suspending saidelectrode means from said vertical column into said slag layer,maintaining said electrode means in said slag layer while passing anelectric current through said electrode means, thereby remelting saidelectrode means by generating heat, moving a first lower mold of saidtwo molds upwardly jointly with said electrode means along said verticalcolumn until said lower mold comes into contact with the second uppermold of said two molds while the molten metal in said first moldsolidifies, and moving thereafter said second mold upwardly jointly withsaid electrode means along said vertical column, whereby a solid unitaryingot is formed having at least one change in crosssectional areadimensions.
 2. A process as set forth in claim 1, in which said metal issteel.
 3. A process as set forth in claim 1, in which said two moldshave inner cylindrical surfaces of different diameters.
 4. A process asset forth in claim 1, in which said electrode means consist of a singleelectrode.
 5. A process as set forth in claim 1, in which at least threemolds are movably suspended from said vertical column.
 6. A process asset forth in claim 1, which comprises removing said electrode means fromone of said molds, cooling said molten metal in said one mold at a firstrate until said molten metal in said one mold has solidified to form aningot portion, and cooling said ingot portion at a second rate, which islower than said first rate.
 7. A process as set forth in claim 6, inwhich cold water is used to cool molten metal in said one mold at saidfirst rate, and warm water is used to cool said ingot portion at saidsecond rate.
 8. A process as set forth in claim 1, which comprisesremoving said electrode means from one of said molds, cooling saidmolten metal in said one mold until said molten metal in said one moldhas solidified to form an ingot portion, and maintaining said ingotportion at a predetermined temperature.
 9. A process as set forth inclaim 8, which comprises applying split insulation to said ingot portionto maintain it at said predetermined temperature.
 10. A process as setforth in claim 9, which comprises heating said insulation while it isapplied to said ingot portion.
 11. A process as set forth in claim 1,which comprises removing said electrode means from one of said molds,cooling said molten metal in said one mold until said molten metal insaid one mold has solidified to form an ingot portion, and applyingunheated, split insulation to said ingot portion.
 12. In an apparatusfor casting molten metal derived from metallic electrode means extendinginto a liquid slag layer through which an electric current is passed, anarrangement comprising a vertical column, at least two molds movablysuspended for independent movement on said vertical column, said twomolds having different cross-sectional area dimensions, means for movingsaid metallic electrode means movably mounted on said column andsupporting said electrode means so that it extends into said liquid slaglayer, means for moving said two molds comprising means for moving afirst lower mold of said two molds upwardly jointly with said electrodemeans along said vertical column until said lower mold comes intocontact with the second mold of said two molds while the molten metal insaid first lower mold solidifies and means for moving said second moldupwardly jointly with said electrode means along said vertical columnwhereby a solid unitary ingot is formed having at least one change incross-sectional area dimensions.
 13. The arrangement as set forth inclaim 12, which comprises a bottom plate disposed under said molds, saidmeans foR moving said molds including a plurality of mold-liftingcarriages, each of which carries one of said molds, said means formoving said electrode means including an electrode-lifting carriagedisposed over said mold-lifting carriages and carrying said electrodemeans, and tension cable means operable to control the vertical movementof said mold-lifting carriages and said electrode-lifting carriageindependently of each other along said vertical column
 14. Thearrangement as set forth in claim 13, including cooling means which areoperatively mounted on said two molds and which are operable to coolsaid molds with a liquid.
 15. The arrangement as set forth in claim 12,in which at least one of said molds is split and adapted to be swungopen.